1. Field
The present invention relates to an image processing device and an image processing method which output a saliency measure of an image.
2. Related Art
Image processing devices, known in a conventional image processing field, detect (extract) a saliency region from an image; the saliency region is a notable image region or an image region to which people would pay attention. Such a saliency region detecting technique is also used to calculate saliency measures for pixels in an image and to create a saliency map that indicates these saliency measures.
One exemplary application of the technique above is to detect a subject from an image.
Learning-based algorithms are used to detect the saliency regions. To give an example, Japanese Unexamined Patent Publication No. 2001-236508 (disclosure date: Aug. 31, 2001) describes a technique for extracting features of various parts from target image data in which saliency measures are to be calculated. This extraction is based on feature types of the parts to be extracted which have been learned and determined in advance through learning-target image data. This technique enables saliency measures to be judged in a manner similar to a human sense by substituting the learning effect for the degree of a human's experience or memory.
Learning-based algorithms as described above are required to prepare leaning-target image data as previous knowledge for target image data. Therefore, without this previous knowledge, saliency measures cannot be evaluated.
To give another example, Japanese Unexamined Patent Publication No. 2010-258914 (disclosure date: Nov. 11, 2010) describes a technique for detecting saliency regions without the need for previous knowledge. In this technique, information between frames making up video is used.
The technique described above does not need any previous knowledge, but is intended only for moving images each made up of multiple frames. Thus, it is not applicable to evaluate saliency measures of still images.